1. Field of Invention
The invention relates to a magnetic position sensing structure and an arrangement method thereof. In particular, the invention relates to a magnetic position sensing structure for an iris diaphragm actuator and an arrangement method thereof.
2. Related Art
Technological advances lead to higher demands for image capturing and processing. Conventionally, the iris diaphragm using a magnet and a magnetic position sensor to convert the magnetic flux sensed by the magnetic position sensor into a voltage output signal. However, a linear relation can not be obtained between the magnetic flux (or voltage) and the position of the magnet owing to inappropriate arrangement of the structure. Therefore, it is necessary to use a nonlinear driving device or a calibration method to adjust to obtain a linear relation, which increases the complexity and the cost of the structure. Alternatively, a plurality of magnets are applied in changing so as to adjust the magnetic flux sensed by the magnetic position sensor into a linear relation. However, this also increases the complexity and the cost of the structure.
FIGS. 1A and 1B show a conventional magnetic position sensing structure using a magnet 11 and a Hall sensor 12. When the magnet 11 moves along a motion direction, the distance “d” decreases and the magnetic flux density increases. However, the magnetic flux density and the distance “d” have a nonlinear relation.
FIGS. 2A and 2B show another conventional magnetic position sensing structure using a magnet 11 and a Hall sensor 12. When the magnet 11 moves along a motion direction, the distance “d” decreases and the magnetic flux density increases. However, the magnetic flux density and the distance “d” also have a nonlinear relation.
FIGS. 3A and 3B show a magnetic position sensing structure using two magnets 11 and a Hall sensor 12. When the Hall sensor 12 moves along a motion direction, the relation between the magnetic flux density and the distance “d” is more linear than the previous two examples in FIGS. 1A and 2A. However, because there are required more magnets, this results in a more complex structure and higher cost.
FIGS. 4A and 4B show a magnetic position sensing structure using four magnets 11 and a Hall sensor 12. When the Hall sensor 12 moves along a motion direction, the relation between the magnetic flux density and the distance “d” is more linear than the previous two examples in FIGS. 1A and 2A. However, even more magnets are used, and likewise, it has a more complex structure and higher cost.
It is therefore an important subject to provide an iris diaphragm actuator, a magnetic position sensing structure, and an arrangement method thereof that have simple structures, easy manufacturing processes, high production yield, low product costs, and no product variations.